Components are widely used for managing distributed applications because they not only capture the software architecture of managed applications as an assembly of components but also permit to dynamically adapt these applications to changing environments. Following this approach, our practical experience in the Jade environment about developing an autonomic repair management service with a self-healing behavior shows novel requirements on reflective component models for architecture-based management systems. First, we have identified five essential runtime abstractions that a component model must include in order to efficiently support an autonomic repair service. Second, our experience suggests that traditional reflective component models should be extended to allow specializing meta-operations. Third, our experience also shows that a meta-data checkpointing capability is best-suited for meta-data recovery after failures. We demonstrate the soundness of these findings in several ways. We applied the difficult problem of autonomic repair to both J2EE and JMS middleware. We further stressed our algorithms and mechanisms by applying them recursively towards gaining a self-healing property for the repair service itself. Although our experience was done in the Jade context, using the Fractal component model, we believe our findings to be general to architecture-based management systems using reflective component models.
With the development of Internet-based business, Web applications are becoming increasingly complex. The J2EE specification aims at enabling the design of such web application servers. These servers have to ensure scalability and availability of the supported applications. Scalibility can be achieved using replication techniques or partitionning techniques. The aim of this paper is to compare these approaches. In a J2EE web application server, one important component is the EJB tier. In this context, the JOnAS web application server provides an example of EJB replication system called CMI (Cluster Method Invocation). In a first step, this paper presents a performance evaluation of CMI. It then introduces incrementally an alternative scheme based on partitionning and shows the performance benefits compared to CMI.
Autonomic computing enables computing infrastructures to perform administration tasks with minimal human intervention. This wrap-up paper describes the experience we gained with the design and use of JADE-an architecture-based autonomic system. The contributions of this article are, (1) to explain how JADE provides autonomic management of a distributed system through an architecture-based approach, (2) to explain how we extended autonomic management from traditional self behaviors such as repairing or protecting a managed system to self-self behaviors where JADE also fully manages itself as it manages any other distributed system, (3) to report on our experience reaching self-self behaviors for two crucial autonomic properties, repair and protection.
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